What are the classifications of accumulators

To prevent gas from entering the hydraulic oil, the gas must be isolated from the hydraulic oil. There are three types of methods: airbag type, diaphragm type, and piston type.

1) Airbag accumulator

Airbag type energy accumulators can have a large capacity, currently available in the market up to 450L, with a maximum working pressure of up to 100MPa.

Airbag accumulator a) Structure b) Initial condition c) When compressed d) After the airbag is compressed 1) One airbag 2) One housing 3) One opening and closing valve A, One air port B, One oil port

The ratio of maximum working pressure to pre inflation pressure, also known as compression ratio. The compression ratio of airbag type accumulators generally does not exceed 4.

Due to minimal wear and long lifespan, airbags can be replaced if damaged, making them currently the most widely used.

2) Diaphragm accumulator

The diaphragm type accumulator is roughly shown in Figure 8-23.

Figure 8-23 Diaphragm Accumulator a) Appearance b) Internal Structure 1- Opening and Closing Valve 2- Diaphragm 3- Shell A – Air Port B – Oil Port

The working volume is generally 0.07-5L, and the maximum working pressure can reach over 35MPa. The compression ratio generally does not exceed 8. Its dynamic response characteristics are generally higher than other types of accumulators.

The compression ratio of airbag and diaphragm type accumulators is low, mainly limited by the deformation capacity of the airbag and diaphragm.

3) Piston accumulator

Due to the absence of deformation components, the compression ratio of piston type accumulators (see Figure 8-24) can theoretically be infinitely high. Thus obtaining a higher energy density. But in fact, due to the limitation of shell strength, the maximum working pressure is currently 80MP2a and the maximum volume is 1200L.

Piston accumulator (Parker) a) Appearance b) Internal structure 1- Sealing ring 2- Piston A – Air port B – Oil port

Due to high requirements for the roughness of the inner wall surface of the shell, the manufacturing cost is relatively high.

4) Precautions

Due to the wear and tear of the seal, which can lead to leakage, regular inspections are necessary. If a sensor is used to monitor the position of the piston from the outside and compare it with the pressure, it can be determined online whether there is any air leakage. The inertia of the piston is generally relatively large and is affected by sealing friction, resulting in slightly poor dynamic response performance and pressure hysteresis.

Accumulators are quite heavy when storing a large amount of energy. Therefore, it will have an undeniable impact on the overall weight and component layout of the machine. For example, according to research and development reports, there is approximately 280000J of energy required for the boom descent of a 20t excavator. To fully recover it, a minimum of 50L accumulator weighing approximately 150kg is required.

Currently, research is underway on how to reduce the accumulator. For example, using high-strength carbon fiber winding technology can reduce the weight of the shell by half or even nine tenths.

What are the classifications of accumulators

To prevent gas from entering the hydraulic oil, the gas must be isolated from the hydraulic oil. There are three types of methods: airbag type, diaphragm type, and piston type.

1) Airbag accumulator

Airbag type energy accumulators can have a large capacity, currently available in the market up to 450L, with a maximum working pressure of up to 100MPa.

Airbag accumulator a) Structure b) Initial condition c) When compressed d) After the airbag is compressed 1) One airbag 2) One housing 3) One opening and closing valve A, One air port B, One oil port

The ratio of maximum working pressure to pre inflation pressure, also known as compression ratio. The compression ratio of airbag type accumulators generally does not exceed 4.

Due to minimal wear and long lifespan, airbags can be replaced if damaged, making them currently the most widely used.

2) Diaphragm accumulator

The diaphragm type accumulator is roughly shown in Figure 8-23.

Figure 8-23 Diaphragm Accumulator a) Appearance b) Internal Structure 1- Opening and Closing Valve 2- Diaphragm 3- Shell A – Air Port B – Oil Port

The working volume is generally 0.07-5L, and the maximum working pressure can reach over 35MPa. The compression ratio generally does not exceed 8. Its dynamic response characteristics are generally higher than other types of accumulators.

The compression ratio of airbag and diaphragm type accumulators is low, mainly limited by the deformation capacity of the airbag and diaphragm.

3) Piston accumulator

Due to the absence of deformation components, the compression ratio of piston type accumulators (see Figure 8-24) can theoretically be infinitely high. Thus obtaining a higher energy density. But in fact, due to the limitation of shell strength, the maximum working pressure is currently 80MP2a and the maximum volume is 1200L.

Piston accumulator (Parker) a) Appearance b) Internal structure 1- Sealing ring 2- Piston A – Air port B – Oil port

Due to high requirements for the roughness of the inner wall surface of the shell, the manufacturing cost is relatively high.

4) Precautions

Due to the wear and tear of the seal, which can lead to leakage, regular inspections are necessary. If a sensor is used to monitor the position of the piston from the outside and compare it with the pressure, it can be determined online whether there is any air leakage. The inertia of the piston is generally relatively large and is affected by sealing friction, resulting in slightly poor dynamic response performance and pressure hysteresis.

Accumulators are quite heavy when storing a large amount of energy. Therefore, it will have an undeniable impact on the overall weight and component layout of the machine. For example, according to research and development reports, there is approximately 280000J of energy required for the boom descent of a 20t excavator. To fully recover it, a minimum of 50L accumulator weighing approximately 150kg is required.

Currently, research is underway on how to reduce the accumulator. For example, using high-strength carbon fiber winding technology can reduce the weight of the shell by half or even nine tenths.

But some mobile machinery itself requires counterweights, such as forklifts, cranes, etc; Some do not require a quick start, such as aircraft tractors, and if the energy storage device is heavier, the problem is not significant.

Life experience shows that after using a pump to inflate bicycle tires, the pump will heat up. This is because when a gas is compressed, not only does the pressure increase, but the temperature also increases. As the heat dissipates, the temperature decreases, and the pressure also decreases. So, in order to achieve high energy efficiency by using energy storage devices, attention should also be paid to insulation measures.